Molecular theory of smectic ordering in liquid crystals with nanoscale segregation of different molecular fragments

Maxim Gorkunov, Mikhail Osipov, Nadja Kapernaum, Dorothee Nonnenmacher, Frank Giesselmann

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

A molecular statistical theory of the smectic A phase is developed taking into account specific interactions between different molecular fragments which enables one to describe different microscopic scenario of the transition into the smectic phase. The effects of nanoscale segregation are described using molecular models with different combinations of attractive and repulsive sites. These models have been used to calculate numerically coefficients in the mean filed potential as functions of molecular model parameters and the period of the smectic structure. The same coefficients are calculated also for a conventional smectic with standard Gay-Berne interaction potential which does not promote the segregation. The free energy is minimized numerically to calculate the order parameters of the smectic A phases and to study the nature of the smectic transition in both systems. It has been found that in conventional materials the smectic order can be stabilized only when the orientational order is sufficiently high, In contrast, in materials with nanosegregation the smectic order develops mainly in the form of the orientational-translational wave while the nematic order parameter remains relatively small. Microscopic mechanisms of smectic ordering in both systems are discussed in detail, and the results for smectic order parameters are compared with experimental data for materials of various molecular structure.
LanguageEnglish
Article number051704
Number of pages13
JournalPhysical Review E: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics
Volume84
Issue number5
DOIs
Publication statusPublished - 21 Nov 2011

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molecular theory
Segregation
Liquid Crystal
Order Parameter
Fragment
liquid crystals
fragments
Calculate
Coefficient
Interaction
Free Energy
coefficients
Experimental Data
Model
Scenarios
molecular structure
free energy
interactions

Keywords

  • liquid crystals
  • smectic
  • nanoscale segregation

Cite this

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title = "Molecular theory of smectic ordering in liquid crystals with nanoscale segregation of different molecular fragments",
abstract = "A molecular statistical theory of the smectic A phase is developed taking into account specific interactions between different molecular fragments which enables one to describe different microscopic scenario of the transition into the smectic phase. The effects of nanoscale segregation are described using molecular models with different combinations of attractive and repulsive sites. These models have been used to calculate numerically coefficients in the mean filed potential as functions of molecular model parameters and the period of the smectic structure. The same coefficients are calculated also for a conventional smectic with standard Gay-Berne interaction potential which does not promote the segregation. The free energy is minimized numerically to calculate the order parameters of the smectic A phases and to study the nature of the smectic transition in both systems. It has been found that in conventional materials the smectic order can be stabilized only when the orientational order is sufficiently high, In contrast, in materials with nanosegregation the smectic order develops mainly in the form of the orientational-translational wave while the nematic order parameter remains relatively small. Microscopic mechanisms of smectic ordering in both systems are discussed in detail, and the results for smectic order parameters are compared with experimental data for materials of various molecular structure.",
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Molecular theory of smectic ordering in liquid crystals with nanoscale segregation of different molecular fragments. / Gorkunov, Maxim; Osipov, Mikhail; Kapernaum, Nadja; Nonnenmacher, Dorothee ; Giesselmann, Frank.

In: Physical Review E: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics , Vol. 84, No. 5, 051704, 21.11.2011.

Research output: Contribution to journalArticle

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AU - Gorkunov, Maxim

AU - Osipov, Mikhail

AU - Kapernaum, Nadja

AU - Nonnenmacher, Dorothee

AU - Giesselmann, Frank

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AB - A molecular statistical theory of the smectic A phase is developed taking into account specific interactions between different molecular fragments which enables one to describe different microscopic scenario of the transition into the smectic phase. The effects of nanoscale segregation are described using molecular models with different combinations of attractive and repulsive sites. These models have been used to calculate numerically coefficients in the mean filed potential as functions of molecular model parameters and the period of the smectic structure. The same coefficients are calculated also for a conventional smectic with standard Gay-Berne interaction potential which does not promote the segregation. The free energy is minimized numerically to calculate the order parameters of the smectic A phases and to study the nature of the smectic transition in both systems. It has been found that in conventional materials the smectic order can be stabilized only when the orientational order is sufficiently high, In contrast, in materials with nanosegregation the smectic order develops mainly in the form of the orientational-translational wave while the nematic order parameter remains relatively small. Microscopic mechanisms of smectic ordering in both systems are discussed in detail, and the results for smectic order parameters are compared with experimental data for materials of various molecular structure.

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